Lot’s of good stuff in this piece, but here’s a few highlights for the time-challenged reader (for whom the long symphony-like standards are too long anyway):

The fact is, progressive rock is nearly indefinable. Even those credited with making progressive rock reject the title as often as not. Prog fans, too, obsess over what group or album or (less likely) song is or is not progressive. Once there’s some semblance of an agreement as to prog quality, the fans then obsess over what type of progressive rock the group or album in question is: symphonic; proto-; crossover; metal; post-; folk; math; space; fusion; Kraut; Canterbury. . .

[W]hile in its specifics prog is fully open to music from all times and all places, the world over, progressive rock generally is very European in its structure and in the atmosphere it creates. Because progressive rock has always tended to sidestep or ignore blues-based rock, mainstream periodicals such as Rolling Stone and journals of opinion such as the New York Times have assumed progressive rock is a betrayal of progressive culture rather than an embracing or enhancing of it. After a very short flirtation with prog, music critics rejected the genre as pretentious and over-the-top. . .

Perhaps the most important aspect of progressive rock is found in this fourth point. Progressive rock does not aim to move the heart or the passions in the way most rock music does. Instead, it aims to harmonize soul and mind and connect the horizontal to the vertical, the sea to the sky. It invites the listener in as a participant, immersing him fully into the art rather than placing the art (if most pop music can be called art) next to or near the listener.

As such, progressive rock is to rock music what Imagism (e.g., T. E. Hulme and T. S. Eliot) is to poetry. It takes a modern form, and it fills and animates it with a well-ordered soul, an essence commensurate with its form.

But again, prog rock is not easily defined. A fifth and final point about its definition is this: Progressive-rock concepts rarely can be explained in the span of a two- or three-minute song. Genesis took 94 minutes to tell the story of Rael in The Lamb Lies Down on Broadway; Rush took 21 minutes to tell the story of failure to resist tyranny in “2112”; Jethro Tull needed 44 minutes for the story of Gerald Bostock in Thick as a Brick; Marillion took 71 minutes to reveal a suicide in Brave; and Big Big Train took 58 minutes for a man to die and examine his life in The Difference Machine.

Read the whole thing, as they say; there’s lots more here. And fire away, readers. (And I still say Brad badly needs to catch up to Gentle Giant.)